An aircraft comprises systems allowing the detection of a potential overheating of an element, such as an engine or a nozzle, where said overheating may be linked to an anomaly, for example a fire. It is common to use temperature sensors comprising a eutectic. A eutectic is a mixture of two pure bodies which melts and solidifies at a constant temperature, for example a mixture of water and salt. Such a mixture therefore goes from the solid state to the liquid state, and vice versa, at a predefined temperature. A sensor may take the form of a cable, comprising a conducting core and an envelope, which is also conducting. Inside of this cable, a eutectic is present between the core and the envelope. This eutectic is typically an electrical insulator when it is in the solid state, and becomes an electrical conductor in the liquid state. A water and salt mixture is commonly used, which mixture is an electrical conductor in the liquid state, the conductivity depending on the proportion of salt in the mixture. The central core is typically made of nickel, and the external envelope is typically a superalloy, in other words an alloy containing a large quantity of nickel and of chrome. An electrical voltage, typically a low-frequency alternating voltage, is applied between the central core and the external envelope. When the eutectic is in the solid state, no current can flow, the eutectic being an electrical insulator in this state. On the other hand, when a section of the cable is heated to a temperature such that the eutectic contained within the cable goes into the liquid state, an electrical current can flow between the central core and the external envelope. It is thus possible to detect this electrical current and to deduce from this that at least one section of the cable is being subjected to a temperature higher than the temperature of fusion of the eutectic.
This type of overheating detector, using a eutectic, has numerous drawbacks. First of all, the installation of such sensors in an aircraft poses numerous constraints owing to the rigidity of the detector cables. This rigidity is inherent to the necessity of having a central core and an external envelope composed of an electrically conducting material that can withstand high temperatures, very often a quite inflexible metal material. These cables thus frequently have constraints on the radius of curvature that they can take, particularly as regards the connectors allowing their connection to the overheat detection system. Such sensors must also be installed taking into account a potential expansion of the elements onto which they are mounted. On the other hand, the eutectic included in the sensor must be designed to withstand the environmental conditions specific to an aircraft, particularly vibrations. More generally, such sensors do not reveal at which point of the detector cable the overheating has occurred. Such sensors do not allow an overheating to be localized more precisely than on the cable, which may potentially be quite long.
It is therefore necessary to provide a system allowing these drawbacks to be overcome.